Optical system for measurement and control



Sept. 16, 1958 C. A. DAVENPORT ETAL OPTICAL SYSTEM FOR MEASUREMENT AND CONTROL Filed March 10, 1954 Fig. 3.

2 Sheets-Sheet 1 CLARENCE A Own/Pom AND CARL C. DALY ATTORNEY.

Sept. 16, 1958 C. A. DAVENPORT ETAL OPTICAL SYSTEM FOR MEASUREMENT AND CONTROL Filed March 10, 1954 2 Sheets-Sheet 2 IN V EN TORS CLARENCE A. DAVENPORT A/vo CARL C. DALY ATTORNEY.

United States Patent '2 4 Claims. (Cl. 250-237) Da Mo., as'signors to Glarence A. Davenport,

This invention pertains to an optieal system tor use in setting up automatic measurement or control iaoilities, such, for instance, as may be used in industrial operations for measuring quantity or quality values of industrial products, detecting and indicating critical conditions in such operations or products, providing safety protection for apparatus, and other applications.

An object of this invention is to provide means for forming alight beam into a broad, thin beam providing in eiiect a sheet of light extending across an active area wherein the effect to be measured takes place.

Another object is to provide, in combination with such me n f m a sheet f l ht m ns f r r cting th light, after it has passed the active area, onto a photosensitive unit which is connected to actuate means for measuring items passing the active area, and/or controlling the operation of a machine or apparatus involved in processing such items.

vOne embodiment of this invention described herein and illustrated in the accompanying drawings is applied to a safety device for industrial machines to insure that the operators hands are out of danger before the machine may be put into operation. Another is applied to the measurement of a flowing fluid.

Generally stated, the embodiments of the invention described, herein include an elongated light source and a lens arranged to direct the light" in a wide, thin beam. This vbeam is then passed through a bank of parallel, closely spaced, nonrefieeting bafljes which confines the beam to substantially parallel rays. The beam so formed is then projected across the active area. A second bank of similar battles is placed beyond said area in'a window of a dark chamber and serves 'to permit the beam to enter the chamber but to shut out extraneous light. Within the dark chamber means are provided to direct all the light of the beam upon a photo-sensitiveunit which is connected to operate the controls of a machine or an ndi ator for measurement, .so that w en y bst ntial amount of ligh isin ermpted in t e activ a, as, nv the fi st ca e. y heope ator moving h s han o hat a he ha e in i y of the light re chi t e pho sens t v un t wi l cause t t s p the ma e- 'I t s ac ompanying drawin s:

F gur 1 i front view of a safety device emb dyi this n e t on. with the covers of the light boxe remove nd par in section,

F gur 2 s a section on ne 2 -2 of 1. but wi h the over n place.

Figure 3 is a section on line 3-3 of Fig. 1, Figure 4 is a section on line4==4 of Fig. 1, igu e 5 s a diasr m is i PIPli view showin an ran em n f r aqn tarins or m asur n a flowin fluid.

2 or bed of a machine to be protected, and the active area is the area above the middle portion of this table (considered in a vertical plane) through which the operator mustmove his hands in loading and unloading the machine or adjusting the workpiece or material operated upon. Mounted on the table 1 to one side of the active area is a light box 2, which may be considered the transmitting box, in which'a light source 3 is mounted. I The light source 3 is shown as an elongated lamp, whiehmay be of the ineandesgent-filament type or other type, such as a fluorescent lamp or the like. T his lamp may be connected to a suitablesupply circuit, not shown.

When a filament-type lamp 3 is used an elongated cylindrical lens '7 may be mounted in parallel relation thereto to form the light into a wide beam of horizontally parallel rays. This beam is projected through a window .4 in the end of the box 2. Between the lens 7 and the window 4 is a bank 5 of parallel baffle plates 6. These bafiles may he of metal, cardboard, or other suitable .opaque material, and have blackened surfaces to make them non-reflecting. They are mounted in parallel relation sos that light may pass through the bank 5 between the 'baflles in the horizontal direction as shown in Fig. 1.

The-lens 7 is so positioned with relation to the lamp 3as torefract the light therefrom into a beam of parallel rays passing through the bank 5 and out at the window 4 tosbe projected across the active area toward the right in a beam of substantially uniform intensity.

,Tjhelight of the lamp3 is thus formed into a wide, beam of substantially parallel rays. The vertical width of this beamsis represented by the height of the Window 4 indicated by'the broken lines A and B in Fig. 1, and its horizontalthickness is the width of the ,window 4, indicated by the broken lines C and Din Fig. 2. The rays, after passing the lens 7, are substantially parallel in .any horizontal plane, and all the rays which deviate subactive area rtethe box .2 is a. second light box 8 pro- ,yided on the side faging the box 2 with a window 9. of

substantially the same shape and size as the window ,4.

lMounted in the window 9 is a bank 10 of bafijl plates 11 Qt cons u ti n sim la to h o h a k Th x .8 may be co id d the l -re e in b x. nd, is posit ned so th the beam Qf'l s t iss in fr m t e w ndow .4. sita ss ng across the a i t am r e W n w fiaad a r th ugh h bank 10 t hs e (r ht, his- 1) of the box 8. The box 8 provides, when its cover'is in p ac a dark shsmherin c h ch he l h of e b insy eate but rom ich he ha les 11 shu out ast ane u li htz 55 as aslest ui rho o tu e or h lik an a so a con- -cave mirror 13 positioned to reeeive the beam of light and concentrate t upon, the un t t is p ef rable that" sub tan ll al thsi ht of h b a he directe u on t e unit 1.2 s n t st i t resp nds in a co dance wit Mou ted in ox 8 1s a hot -sens tive ni v12., such the intens t f the i h falling upon it and, erefore, any r du tion, Qt uch intsllsit ii/ nterc p ng any bstant al Parf the beans wil 'cau e a corre pon sn a s y said uni A lens may e used in p ace o h j hi tsr t9 scas nt sts the. gh b for h p sen embo iments mi ror i pretensi- The response of the unit 12 to changes of light intensity may be used to actuate controls in any suitable manner. Figure 8 is a diagram of a circuit which may be used. The unit 12 may be connected to a suitable supply circuit 14 through suitable control resistors 15, 16, 17, and 18, and connected to the grid of a relay tube 19, a

gas tetrode, supplied through a transformer 20 from the circuit 14. The tube 19 controls a relay 21 which is connected in any suitable manner to control the power supply of the machine 1. Thus any reduction in the intensity of illumination of the unit 12 will cause it to change the grid bias of the tube 19 so as to cause the latter to open the relay 21 to stop the machine.

Figure 7 shows a modified form of bafiie which may be used in the banks and 10. In this arrangement the baflle plates 22 are assembled to form hexagonal tubes as shown. Other polygonal shapes, such as squares, rectangles, triangles, etc., may of course be used to form the tubes.

In the use of this device the boxes 2 and 8 are mounted on the machine on opposite sides of the active area as indicated in Figs. 1 and 2. The covers of these boxes, 23 and 24 respectively, are put in place so as to shut out all light except that of the lamp 3. Said lamp is turned on and the circuit of Fig. 8 adjusted to the desired condition of response. Thereafter, so long as any part of the operators body, or any other object, intercepts light of the beam between A, B, C, and D the circuit of the power drive of the machine will be held open. As soon as the object is withdrawn so as to complete the beam, said circuit will be conditioned for operation. It will be noted that interception of light in any part of the beam will affect the unit 12, since light rays traverse every part of the beam and there are no blind spots. And since substantially all the light reaches the unit 12, interception of any substantial part of it will cause said unit to respond.

The same, or a similar arrangement, may be applied to automatic apparatus wherein a part of the machine, instead of the operators hands, moves into the active area to perform preliminary operations. The movement of such part through the light beam will control the operation of the safety mechanism.

In the embodiment illustrated in Fig. 5 the boxes 2 and 8 are set up in the same relative positions as in Fig. 1 so that the light beam passing between the windows 4 and 9 defines the active area. Means are provided, in the form of a conduit 25, for conducting a fluid through the active area. This may be a gas or a liquid. This conduit may be provided with windows 26 and 27, aligned with the windows 4 and 9, to permit the light to pass through the flowing fluid. The varying intensity of the light falling on the unit 12 will then be a measure of the density of smoke or dust carried by a gas, the turbidity of a liquid or changes in the color thereof, and other effects depending upon the amount of light interrupted by the material passing through the active area. The response of the unit 12 may be used, as in Fig. 8, to control mechanism, or for measurement, in which case therelay 21 would usually be replaced by a measuring instrument.

In a similar manner other items than fluids may be passed through the active area. Solid items may be so passed, as by a mechanical conveyor in the place of the conduit 25, and such items may be counted or, if items of different sizes are passed, they may be counted and also classified according to size.

Where color values are involved a color screen 28 may be placed across the window 4 to color the issuing light correspondingly. For example, in the safety device of Fig. 1, if a red screen 28 is used with a red-sensitive unit 12, if the operator happens to be smoking the smoke blown through the active area will not afiect the operation since red light penetrates smoke very effectively. On the other hand, smoke density may be measured, with the arrangement of Fig. 5, by using a blue screen and a bluesensitive unit 12.

The active area may of course be extended to any desired magnitude, and the beam may be redirected by means of mirrors to form a fence of light partially or wholly enclosing a given region, and any item entering or leaving that region through the beam will cause a response by the unit 12;

Changes may be made in the details of construction, within the scope of the appended claims, without departing from the spirit of this invention. Parts of the invention may be used without the Whole and improvements may be added while retaining some or all of the advantages of the invention.

Having thus described the invention, what is claimed 1s:

1. In a safety device of the character described, an optical system comprising, an elongated continuous light 7 source, an elongated cylindrical lens in parallel relation to the light source, a window, thin bafiles in said window directing the light in a substantially uniform beam for the length and width of the window, said beam being directed across the active area of a machine, a single photosensitive unit, means in the path of said beam after passing said area operating to direct substantially all the light of the beam on said unit, and means controlled by said unit controlling the operation of the machine.

2. In a protective system for a machine, means for projecting a beam of light of substantially uniform intensity across the bed of the machine, a series of light baffles on said projecting means, a transparent red screen on said series of bafiies, a dark box having a window adapted to admit light from substantially one direction only, a second series of bafiles in said window, a single photosensitive unit in said box, said unit photosensitive selectively to red light only, means for concentrating the light on said unit, and connections to said unit controlling the operation of the machine. 7

3. In an optical system for the control of a machine, means for projecting a monochromatic light sheet of substantially unform luminosity, a dark box having a window, a series of light baflies arranged in said window so as to admit said sheet of light edgewise from substantially one direction only, a single photosensitive unit in said box, said photosensitive unit having a selective re sponse to said monochromatic light, means for concentrating substantially all the light entering by said window on said photosensitive unit, and electrical connections to said photosensitive unit controlling the operation of said machine.

4. A device as in claim 3 in which the baffles in said window are in the form of tubes.

References Cited in the file of this patent UNITED STATES PATENTS 1,922,188 Zworykin Aug. 15, 1933 1,940,882 Rich Dec. 26, 1933 1,958,128 Cate May 8, 1934 1,962,742 Iongedyk June 12, 1934 2,082,941 Burnside June 8, 1937 2,216,716 Withem Oct. 1, 1940 2,346,240 Thomas Apr. 11, 1944 2,361,235 Pick Oct. 24, 1944 2,442,240 Hooker et al. May 25, 1948 2,550,610 Smith et al. Apr. 24, 1951 2,615,079 Pardue et al. Oct. 21, 1952 OTHER REFERENCES Walker: Photoelectric Cells in Industry, 1948, Pitman Publishing Corp., New York, pages 184and 185.

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